In general, a fuel cell is a system producing electricity from a chemical reaction of hydrogen and oxygen, as a reverse reaction of an electrolysis reaction of water. The fuel cell is regarded as a highly-efficient and clean energy source, and the use thereof is gradually increasing.
In particular, polymer electrolyte membrane fuel cells (PEMFCs) are operable in a relatively-low temperature and have rapid start and response characteristics, and thus developments thereof for a mobile power source of vehicles are actively being undertaken.
A stack of such a PEMFC is formed by stacking a desirable number of unit cells. Each of the unit cells may include: a membrane electrode assembly (MEA) including an anode, a cathode, and a polymer electrolyte membrane between the anode and the cathode; a gas diffusion layer (GDL); a metal-made separator referred to as a bipolar plate; and a gasket.
Since a single unit cell of a hydrogen-oxygen reaction fuel cell can generate up to about 1.2 volts at an operating temperature of 100° C. or below, a single fuel cell is constructed by stacking a plurality of unit cells in series such that an amount of current required for driving a vehicle can be produced.
FIG. 1 is a view illustrating a unit cell of a fuel cell of the related art fabricated by integrating an MEA and a GDL, and FIG. 2 is a view illustrating a unit cell injection mold for a fuel cell of the related art.
As illustrated in FIGS. 1 and 2, in the related art, a process of fabricating unit cells each having a polymer frame 20 by integrating an MEA and a GDL using a polymer resin 30 in an injection mold was developed.
Here, the injection mold of the related art may include an upper mold 101 having a protrusion 301 and a lower mold 201 having a protrusion 301 facing the protrusion 301 of the upper mold 101. The opposing protrusions 301 of the upper and lower molds 101 and 201 prevent the polymer resin 30 from permeating into an insert 10 in which the MEA and the GDL are integrated.
The above-mentioned protrusions 301 can effectively prevent the polymer resin 30 from permeating into the insert 10 even in a condition in which the pressure of injection is excessive, since the protrusions 301 are formed from the same metallic material as the upper mold 101 and the lower mold 201. However, the insert 10 may be damaged, for example, fractured or cut, by the protrusions 301 formed from the metallic material, since the insert 10 is formed from a relatively softer and smoother material than the metallic material. This increases a defect rate of products, which is problematic.
The foregoing is intended merely to aid in the understanding of the background of the present disclosure, and is not intended to mean that the present disclosure falls within the purview of the related art that is already known to those skilled in the art.